The present invention relates to a seat belt apparatus for use in the restraining of a person on a seat of the vehicle by webbing strap.
The conventional seat belt apparatus is disclosed on the chapter Equipment paragraph 15-3 in the Manual of Vehicle Engineering Vol. 7 Revised Edition, May 31, 1983. The seat belt apparatus described in the above literature is shown in FIG. 5 by a schematic view.
That is, the seat belt apparatus is a seat belt of three point attachment type which is provided with a take-up mechanism 100 secured to the under portion of a center pillar B.sub.1 at the outer side oi a seat S. The take-up mechanism 100 is provided with a webbing strap 101 therein in such a manner that one end oi the webbing strap is secured to the take-up mechanism 100 windably, and the other end of the webbing strap slidably passes through a relay anchor A.sub.1 which is secured to the upper portion oi the center pillar B.sub.1 at the outer side of the seat S and a thrusting tongue T and is secured to an anchor A.sub.2 attached to a floor vehicle body side B.sub.2 at the center side of the seat S.
A buckle B for engaging the tongue T detachably is also secured to the floor B.sub.2, at the center side of the seat S.
This take-up mechanism 100 is so constructed that when it is in a free mode after pulling out the webbing strap 101, the webbing strap 101 is automatically taken up and when, for example, large shock or the like is sensed, the pull-out and take-up operation of the webbing strap is stopped, thereby locking the webbing strap 101 at current pull-out amount thereof.
In this case, the automatic take-up force of the webbing strap 101 by the take-up mechanism 100 is so small that the person does not feel an oppressive sensation in case of taking up the webbing strap.
After sitting on the seat S, person pulls out the webbing strap 101 from the take-up mechanism 100, pulls it across the chest obliquely, across the waist portion and hook on the tongue T to the buckle B, so as to restrain the person on the seat S.
For example, when large shock or the like is sensed, the take-up mechanism 100 stops the pull-out or take-up operation of the webbing strap to hold the condition that the person is restrained on the seat S.
In the above conventional seat belt apparatus, the take-up force of the webbing strap 101 by the take-up mechanism 100 is made so small that the person does not feel an oppressive sensation, and thus when the person moves his body while sitting on the seat S, the webbing strap 101 is also pulled out from the take-up mechanism 100 in accordance with his movement. Then, when the pull out and take-up operation of the webbing strap 101 from the take-up mechanism 100 is stopped by the sensing of the shock or the like in a case where the webbing strap 101 is pulled out by an amount more than the pulled out amount capable of restraining the person on the seat S, the webbing strap 101 remains in the state that it is pulled out over the predetermined amount and becomes lose, and thus it can not restrain the person on the seat S. Even when the webbing strap 101 is pulled out over the predetermined amount thereof, it is desirable that the person may be restrained on the seat S.